id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type 525903846,MDU6SXNzdWU1MjU5MDM4NDY=,3552,Dataset.drop() no longer works with a set as an argument,4179064,closed,0,,,15,2019-11-20T16:08:18Z,2020-01-14T16:13:24Z,2020-01-14T16:13:24Z,NONE,,,,"#### MCVE Code Sample ```python # Your code here #!/usr/bin/env python import xarray import numpy ds = xarray.Dataset() ds['x'] = ('x', numpy.linspace(0., 1., 100)) ds['y'] = ('y', numpy.linspace(0., 1., 50)) print(ds) ds = ds.drop(set('x')) print(ds) ``` #### Expected Output ``` Dimensions: (x: 100, y: 50) Coordinates: * x (x) float64 0.0 0.0101 0.0202 0.0303 ... 0.9697 0.9798 0.9899 1.0 * y (y) float64 0.0 0.02041 0.04082 0.06122 ... 0.9592 0.9796 1.0 Data variables: *empty* Dimensions: (y: 50) Coordinates: * y (y) float64 0.0 0.02041 0.04082 0.06122 ... 0.9592 0.9796 1.0 Data variables: *empty* ``` #### Problem Description In versions before xarray 0.14.1, the code above involving calls to `Dataset.drop()` with a `set` as an argument worked as expected. With the new release, the result is an error as shown below. This is breaking backwards compatibility with our software ([MPAS-Analysis](https://github.com/MPAS-Dev/MPAS-Analysis)). ``` Dimensions: (x: 100, y: 50) Coordinates: * x (x) float64 0.0 0.0101 0.0202 0.0303 ... 0.9697 0.9798 0.9899 1.0 * y (y) float64 0.0 0.02041 0.04082 0.06122 ... 0.9592 0.9796 1.0 Data variables: *empty* Traceback (most recent call last): File ""./drop_issue.py"", line 10, in ds = ds.drop(set('x')) File ""/home/xylar/miniconda3/envs/test/lib/python3.7/site-packages/xarray/core/dataset.py"", line 3643, in drop return self.drop_sel(labels, errors=errors) File ""/home/xylar/miniconda3/envs/test/lib/python3.7/site-packages/xarray/core/dataset.py"", line 3689, in drop_sel labels = either_dict_or_kwargs(labels, labels_kwargs, ""drop"") File ""/home/xylar/miniconda3/envs/test/lib/python3.7/site-packages/xarray/core/utils.py"", line 257, in either_dict_or_kwargs ""the first argument to .%s must be a dictionary"" % func_name ValueError: the first argument to .drop must be a dictionary ``` #### Output of ``xr.show_versions()``
# Paste the output here xr.show_versions() here INSTALLED VERSIONS ------------------ commit: None python: 3.7.3 | packaged by conda-forge | (default, Jul 1 2019, 21:52:21) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 4.15.0-1063-oem machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.5 libnetcdf: 4.7.1 xarray: 0.14.1 pandas: 0.25.3 numpy: 1.17.3 scipy: 1.3.2 netCDF4: 1.5.3 pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.0.4.2 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: 1.3.1 dask: 2.8.0 distributed: 2.8.0 matplotlib: 3.1.2 cartopy: 0.17.0 seaborn: None numbagg: None setuptools: 41.6.0.post20191101 pip: 19.3.1 conda: None pytest: 5.3.0 IPython: None sphinx: None
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3552/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue 399457300,MDU6SXNzdWUzOTk0NTczMDA=,2680,Error importing xarray 0.11.2 in python 2.7,4179064,closed,0,,,1,2019-01-15T17:37:56Z,2019-01-15T19:38:05Z,2019-01-15T19:38:05Z,NONE,,,,"I'm creating a fresh conda environment that's pretty minimal: ```bash conda create -y -n test_env python=2.7 xarray numpy dask conda activate test_env python -c ""import xarray"" ``` I see the following error message:

``` Traceback (most recent call last): File """", line 1, in File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/xarray/__init__.py"", line 10, in from .core.alignment import align, broadcast, broadcast_arrays File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/xarray/core/alignment.py"", line 10, in from . import utils File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/xarray/core/utils.py"", line 16, in from .pycompat import ( File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/xarray/core/pycompat.py"", line 73, in import dask.array File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/dask/array/__init__.py"", line 9, in from .routines import (take, choose, argwhere, where, coarsen, insert, File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/site-packages/dask/array/routines.py"", line 256, in @wraps(np.matmul) File ""/home/xylar/miniconda3/envs/test_env4/lib/python2.7/functools.py"", line 33, in update_wrapper setattr(wrapper, attr, getattr(wrapped, attr)) AttributeError: 'numpy.ufunc' object has no attribute '__module__' ```

If I omit `dask`, I don't see this error. I also haven't had any trouble before this week so it's possible that this is caused indirectly by another library having been updated. #### Expected Output Nothing at all. #### Details of conda environment
Details from conda create

``` conda create -n test_env4 python=2.7 xarray numpy dask Solving environment: done ## Package Plan ## environment location: /home/xylar/miniconda3/envs/test_env4 added / updated specs: - dask - numpy - python=2.7 - xarray The following NEW packages will be INSTALLED: backports_abc: 0.5-py_1 conda-forge blas: 1.1-openblas conda-forge bokeh: 1.0.4-py27_1000 conda-forge ca-certificates: 2018.11.29-ha4d7672_0 conda-forge certifi: 2018.11.29-py27_1000 conda-forge click: 7.0-py_0 conda-forge cloudpickle: 0.6.1-py_0 conda-forge cytoolz: 0.9.0.1-py27h14c3975_1001 conda-forge dask: 1.0.0-py_0 conda-forge dask-core: 1.0.0-py_0 conda-forge distributed: 1.25.2-py27_1000 conda-forge freetype: 2.9.1-h3cfcefd_1004 conda-forge futures: 3.2.0-py27_1000 conda-forge heapdict: 1.0.0-py27_1000 conda-forge jinja2: 2.10-py_1 conda-forge jpeg: 9c-h14c3975_1001 conda-forge libffi: 3.2.1-hf484d3e_1005 conda-forge libgcc-ng: 7.3.0-hdf63c60_0 conda-forge libgfortran-ng: 7.2.0-hdf63c60_3 conda-forge libpng: 1.6.36-h84994c4_1000 conda-forge libstdcxx-ng: 7.3.0-hdf63c60_0 conda-forge libtiff: 4.0.10-h648cc4a_1001 conda-forge locket: 0.2.0-py_2 conda-forge markupsafe: 1.1.0-py27h14c3975_1000 conda-forge msgpack-python: 0.6.0-py27h6bb024c_1000 conda-forge ncurses: 6.1-hf484d3e_1002 conda-forge numpy: 1.16.0-py27_blas_openblash1522bff_1000 conda-forge [blas_openblas] olefile: 0.46-py_0 conda-forge openblas: 0.3.3-h9ac9557_1001 conda-forge openssl: 1.0.2p-h14c3975_1002 conda-forge packaging: 18.0-py_0 conda-forge pandas: 0.24.0rc1-py27hf484d3e_0 conda-forge partd: 0.3.9-py_0 conda-forge pillow: 5.4.1-py27h00a061d_1000 conda-forge pip: 18.1-py27_1000 conda-forge psutil: 5.4.8-py27h14c3975_1000 conda-forge pyparsing: 2.3.1-py_0 conda-forge python: 2.7.15-h938d71a_1006 conda-forge python-dateutil: 2.7.5-py_0 conda-forge pytz: 2018.9-py_0 conda-forge pyyaml: 3.13-py27h14c3975_1001 conda-forge readline: 7.0-hf8c457e_1001 conda-forge setuptools: 40.6.3-py27_0 conda-forge singledispatch: 3.4.0.3-py27_1000 conda-forge six: 1.12.0-py27_1000 conda-forge sortedcontainers: 2.1.0-py_0 conda-forge sqlite: 3.26.0-h67949de_1000 conda-forge tblib: 1.3.2-py_1 conda-forge tk: 8.6.9-h84994c4_1000 conda-forge toolz: 0.9.0-py_1 conda-forge tornado: 5.1.1-py27h14c3975_1000 conda-forge wheel: 0.32.3-py27_0 conda-forge xarray: 0.11.2-py27_1000 conda-forge xz: 5.2.4-h14c3975_1001 conda-forge yaml: 0.1.7-h14c3975_1001 conda-forge zict: 0.1.3-py_0 conda-forge zlib: 1.2.11-h14c3975_1004 conda-forge Proceed ([y]/n)? y Preparing transaction: done Verifying transaction: done Executing transaction: done # # To activate this environment, use # # $ conda activate test_env4 # # To deactivate an active environment, use # # $ conda deactivate ```

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